The major thrust of this study is to elucidate the molecular genetics of neoplastic transformation of normal tissues and the purification and function of two biological modifiers in the cellular defense mechanism. Three experimental systems were used: 1) Two rat retroviruses - a) RHHV, originally isolated in this laboratory and b) WR-RaLV, a wild rat tumor virus; 2) AFB-1 (aflatoxin B-1) interaction with both murine and human DNAs and the subsequent activation of an oncogene; and 3) Interleukin 2 (IL-2), a T-cell product, and CCDF, cytotoxic cell differentiation factor, produced by macrophages for the induction of natural killer (NK)-like cells into cytotoxic cells. (1) Based on our resolved restriction endonuclease map, we have accomplished the sequence of 3500 nucleotides of various RHHV DNA subgenomic fragment(s) that were found active in recombination with the Kirsten murine sarcoma virus (K-MSV) genome in microinjection studies and critical to the evolution of a transforming virus. We have also resolved the sequence for 650 nucleotides of the WR-RaLV genomic DNA that reflected both the divergent and conservative sequences with a Harvey MSV subgenomic DNA clone in heterduplex mapping analysis. (2) The molecular mechanism by which a DNA alkylating agent, AFB-1, activates an oncogene or other cellular genes of both human and murine tissues was investigated. We have identified the human subgenomic DNA fragments of hepatocellular carcinoma that showed preferential binding with AFB-1 at N-7 of deoxyguanine forming DNA-AFB-1 adducts, and one of which shared extensive homology with the Harvey ras (H-ras) gene. (3) We succeeded in isolating and purifying murine IL-2 and CCDF by chemical fractionations and column chromatography including HPLC. Using the purified IL-2 and CCDF, the effects of (a) IL-2 on the induction of suppressor T-lymphocytes and (b) CCDF on the differentiation of NK-like cells into cytotoxic lymphocytes, critical to the immune surveillance of tumor growth, have now been better defined.